Efficient filling and weighing of bulk bags (also known as flexible intermediate bulk containers) is performed with an apparatus on which a bulk bag is suspended by loops above a bag support table. During filling of the bag, the bag bottom is partly supported by the support table, which typically has a top portion shaped like a flattened, truncated pyramid. A pair of unbalanced counter-rotating motors are located inside the support table to vibrate and compact the contents of the bag as it is being filled.
The bag support table is brought into contact with the bulk bag either by lowering the bag or raising the support table. Two types of apparatus in which the support table can be raised and lowered are disclosed in U.S. Pat. Nos. 4,718,464 and 5,336,853. In U.S. Pat. No. 4,718,464, the support table is raised and lowered by a piston and cylinder device attached to the frame of the bag filling apparatus. In U.S. Pat. No. 5,336,853, the support table is raised and lowered by a screw and collar system incorporated into the frame.
To ensure that a bulk bag is filled with the correct amount of material, it may be weighed several times during the filling cycle. In order to accurately weigh the bulk bag, it must be separated from the bag support table. Each time the bulk bag is weighed, the motors in the support table are allowed to wind down, and the bag support table is lowered. As the motors wind down, they lose their synchronization and generate significant vibrational forces on the bag support table. With the support table attached to the frame of the apparatus, these vibrations are effectively absorbed.
However, attachment of the bag support table and the lifting mechanism to the frame prevents the bag support table from being used for retrofit applications, for example to be incorporated into an older style bag filling apparatus not having a bag support table. Therefore, there is a need for a self-contained bag support table which does not rely on the frame of the bag filling apparatus for support or for vibration damping.